March 26 (Bloomberg) -- Exxon Mobil Corp. regained the mantle as the world's biggest company by market value, overtaking PetroChina Co., whose Shanghai shares have plunged 58 percent since surging on their first day of trading in November.

PetroChina dropped for a fifth day, falling 2.5 percent to 18.53 yuan in Shanghai, reducing its market capitalization to about $453 billion. The Chinese company's Hong Kong-traded stock fell 1.3 percent to HK$9.69. Exxon Mobil had a market value of $461 billion as of today's close in New York after rising 14 percent in the past year on record energy prices.

PetroChina, an 8-year-old creation of the People's Republic of China, in November overtook Exxon Mobil, which traces it roots to the 1880s and John D. Rockefeller's Standard Oil Trust. After jumping to $1 trillion, PetroChina's value has fallen by more than half as rig rates climb and price caps keep the company from passing on $100-a-barrel oil costs to motorists.

``PetroChina just doesn't show up in terms of reaping any kind of excess reward for the sort of risk involved in investing in them,'' said Phillip Mitteldorf, a portfolio manager who helps oversee $5 billion at Navellier & Associates Inc. in Reno, Nevada. ``We won't even look at them.''

Exxon Mobil, based in Irving, Texas, rose $1.06, or 1.2 percent, to $86.26 in New York. The company raked in $40.6 billion in profit last year, the most ever for any U.S. corporation. Exxon Mobil's 2007 revenue of $358.6 billion exceeded the gross national products of all but 20 nations.

Five Months at the Top

PetroChina's reign of almost five months as the world's most valuable corporation began when its stock price more than doubled in the first day of Shanghai trading after an offering of 4 billion shares there. As PetroChina lost more than half its market value since then, Exxon Mobil fell less than 1 percent.

The value of all Chinese stocks fell 25 percent this year to $3.36 trillion after more than tripling in 2007. The Standard & Poor's 500 Index, by comparison, this year has dropped 8.7 percent.

Investors who bought PetroChina stock on the expectation that rising energy demand in China's expanding economy would boost the company's refining profit have been disappointed, said James Halloran, an analyst at Cleveland-based National City Private Client Group, which manages $35 billion.

PetroChina's refineries lost $54 million a week last year because government price controls prevented the company from passing higher oil costs on to transport firms and other fuel users. The shares dropped to a 10-month low in Hong Kong when those results were announced on March 20.

Biggest Refiner

Exxon Mobil's refining business, the world's largest, had profit of $184 million a week in 2007. The company sells 80 percent of the fuel it produces in the Americas, Europe and other markets where price controls are less restrictive or non- existent.

``It's government control versus free enterprise and there's no comparison,'' said Jack Aydin, a senior managing director and energy analyst at Keybanc Capital Markets in New York.

PetroChina has also been forced to spend more for drilling rigs, pipes and valves as oil companies around the world compete for limited supplies of equipment needed to find and develop petroleum deposits, said David Foley, who helps oversee $750 million in investments at Grove Creek Asset Management.

PetroChina's costs for drilling wells and building pipelines jumped 30 percent in 2007 to about $36 billion, compared with a 3.1 percent drop in such expenses at Exxon Mobil.

Exxon Mobil has a 29 percent return on capital employed, the highest among the world's biggest 10 oil companies by sales. PetroChina is seventh with a 21 percent return, behind Total SA, Royal Dutch Shell Plc, Chevron Corp., BP Plc and China Petroleum and Chemical Corp., according to data compiled by Bloomberg.

To contact the reporter on this story: Joe Carroll in Chicago at jcarroll8@bloomberg.net.

Last Updated: March 26, 2008 16:16 EDT